Fix edoc error in dvvset.erl
Fix edoc error in dvvset.erl

Remove use of `@title` tag in module.

From the [Edoc User's Guide
0.7.13](http://www.erlang.org/doc/apps/edoc/chapter.html): Specifies a
title for the overview page. This tag can _only_ be used in an overview
file. The content can be arbitrary text.

Kyorai/riak_core